(Supported in part by NIH GM 23484 and R01 GM 49530 to S. Erlandsen). Sterecon is being used at the University of Minnesota for 3-D measurements of immunolabelled cell-surface proteins imaged by high-resolution, low-temperature, low-voltage SEM. 3-D measurements of proteins on the 10nm scale agree with the expected size of the labeled molecules. Measurements have been made on the surfaces of human lymphocytes and bacteria. Sterecon is also being used to measure surface area and flagella length of various pathogenic protozoa. Additional applications in confocal LM and hospital X-ray tomography are anticipated. Dr. Leith modified Sterecon for more convenient use with SEM and confocal images. M. Marko visited UMN to install and test Sterecon, and Dr. Erlandsen visited Albany twice for training. A method for testing and debugging Sterecon applications at remote sites over the Internet was developed.